The encoding of meter readings for use in remote reading telemetry systems is well known. In a utility meter, registers provide a read-out of the total consumption of the measured quantity, such as kilowatt-hours of electrical energy in a watthour meter, by converting the sum of rotations of a meter shaft into calibrated dial readings. Watthour meter registers are typically provided with four or five dials with each dial having an associated pointer shaft, which are dirven by a gear train system from the rotating meter movement. The five dials, for example, have readings in units, tens, hundreds, thousands, and ten thousands of the quantity to be measured, for example, kilowatt-hours. The register has a predetermined ratio constant which is related to the consumption of the quantity to be measured and the rate of rotation of the metering movement produced by thhe consumption of one unit of the quantity to be measured. In an encoding register, the angular position of each of the dial pointer shafts is converted, or encoded, into an electrical binary or digital signal. In remote utility meter reading systems, encoding at the meter permits the electrical signal representation to be compared to the register dial reading at the meter site.
In U.S. Pat. No. 4,037,219 issued July 19, 1977 to Arthur Lewis and assigned to the assignee of this invention, there is disclosed and claimed an optoelectronic meter register encoder wherein a notched pattern disk, or code wheel, is mounted to each of a plurality of pointer shafts. The code wheels actuate photosensitive pick-ups, or photocells, to produce a multiple-bit binary code representation of the angular position of each pointer shaft. In accordance with the known construction of meter registers, the pointer shafts are interconnected by gearing so as to have a predetermined ratio such as a ratio of 1 to 10. In a five dial decade register, the units dial will rotate 10,000 times for a 1/10 incremental rotation of the ten-thousands dial. The thousands, hundreds, and tens dials will be proportionally rotated along with the movement of the lowest and highest order dials.
In the manufacture and maintenance of meter encoding register, it is necessary to precisely establish and maintain the position of each code wheel relative to each pointer shaft with which it is associated. The code wheels are assembled to the shafts, which are then assembled into the register gear train system. Finally the pointers are aligned on the ends of the pointer shafts with respect to the position of the code wheels and the dial indicating position of the pointer.
During manufacture it is necessary to test and adjust the code wheels so that they produce the appropriate electronic coded signal output for indicating the dial position of the shaft and pointer. Although the pointer may be shiftable on the pointer shaft, it is usually desirable to fix the position of the pointer on the shaft so that thereafter no readjusting of the code pattern occurs relative to the shaft and pointer.
Following the testing operation during the manufacturing process, it is necessary to reestablish electrical and mechanical interdial alignment. In some prior art registers, this was accomplished by permanently fixing the alignment at the time of manufacture. However, by permanently fixing the alignment it was also difficult if not impossible to reset the register reading in the field. A major improvement in this situation was achieved throuugh the use of clutch mechanisms on the register shafts, as taught by U.S. Pat. No. 4,072,267, issued Feb. 7, 1978 to Eugene C. Benbow and assigned to the assignee of this invention. Through the use of shaft clutches, each shaft could be independently adjusted and aligned to any desired level of accuracy.
In prior art designs incorporating clutches on the register shafts, resetting of the register to zero was accomplished by reading the shaft position electrically while adjusting the shaft angular position. That is, the electrical signal output of the register encoder was monitored during angular adjustment of each shaft. Since the electrical reading of registers incorporating the teachings of the aforementioned U.S. patents only changed every 18 degrees of shaft rotation and interdial alignment permitted a maximum of 9 degrees of alignment error, problems frequently developed in the alignment procedure. This procedure required the operator to set the dial to a transition point between two electrical readings, such that gear backlash on the register would allow the electrical reading to oscillate between the two readings on either side of the transition point. Since gear backlash was generally less than a few degrees, this procedure permitted alignment well within the 9 degree maximum error.
Although the aforementioned procedure produced satisfactory results, it was impossible to test the alignment on a finished register without going through the entire alignment procedure again. Thus, the skill of the operator was paramount to the success of the interdial alignment operation. Furthermore, the alignment procedure was time consuming, since the operator had to allow a significant period of time between electrical readings to allow the test apparatus to "settle". The alignment procedure was therefore a lengthy process which increased manufacturing cost.
The present invention is directed to the aforementioned difficulties and disadvantages in manufacturing, testing, and maintaining meter encoding registers made in accordance with prior art procedures.